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General Description

The Diabetes Control and Complications Trial (DCCT) was a multicenter, randomized clinical trial designed to compare intensive with conventional diabetes therapy with regard to their effects on the development and progression of the early vascular and neurologic complications of type 1 insulin-dependent diabetes mellitus. The DCCT study involved 1,441 participants, ages 13 to 39, with type 1 diabetes and either no or minimal background retinopathy. Participants were required to have had diabetes for at least 1 year but no longer than 15 years.

Once enrolled, patients were randomized to receive standard therapy, consisting of not more than two injections of insulin per day, or intensive therapy, consisting of either subcutaneous insulin infusion by pump or at least three subcutaneous injections of insulin daily, targeting near-normal glycemia. Both groups received the same dietary management and education program. Blood glucose and hemoglobin A1c measurements were used as primary indicators of metabolic control. The primary outcome measure was diabetic retinopathy. Other outcome measures included diabetic nephropathy, diabetic neuropathy, and cardiovascular events or their known or putative risk factors. The DCCT study found that intensive therapy showed beneficial effects on retinopathy, nephropathy, and neuropathy when compared with conventional therapy.

Following these findings, the Epidemiology of Diabetes Interventions and Complications (EDIC) study was initiated as follow-up to examine the long-term effects of the original DCCT interventions on diabetic complications such as cardiovascular events and advanced retinal and renal disease. Over 90 percent of participants from the DDCT study were followed by the EDIC study. Similar to the DCCT study, glycosylated hemoglobin values, fasting lipid levels, serum creatinine values, and other risk factors for cardiovascular disease were measured at different intervals for participants. Cardiovascular complications were assessed with standardized means and classified by an independent committee. The EDIC study has found that intensive diabetes therapy reduced risk of cardiovascular disease in patients with type 1 diabetes and that the differences in outcomes between the intensive and conventional therapy groups persist after long-term study.

Data from the DCCT study and from the EDIC study up to June 2012 (the end of EDIC Year 19) are available from the Repository. GWAS data may be requested through dbGAP.

Objectives

The DCCT study sought to determine the effects of intensive versus standard diabetes therapy on the development and progression of the early vascular and neurologic complications of type 1 diabetes. Intensive therapy was aimed to maintain blood glucose concentrations close to the normal range in diabetic patients, which was hypothesized to decrease the development and progression of diabetic complications.

The EDIC study aimed to determine the long-term effects of the original DDCT interventions on diabetic complications such as cardiovascular events and advanced retinal and renal disease.

Outcome Measure

The primary outcome measure for the DCCT study was diabetic retinopathy, which was chosen because it can be reliably quantified and its rate of progression determined in a reasonable number of years. Blood glucose and hemoglobin A1c measurements were used as primary indicators of metabolic control. Other outcome measures included diabetic nephropathy, diabetic neuropathy, and cardiovascular events or their known or putative risk factors.

The primary outcome measure for the EDIC study was the time to the first of any cardiovascular disease event. Similar to the DCCT study, secondary outcome measures included assessment of retinopathy, neuropathy, and nephropathy in participants. Notably, as both studies track diabetic nephropathy as an outcome measure, the DCCT and EDIC studies are kidney-relevant.

Criteria

The EDIC study enrolled patients who had previously participated in the DCCT study. The DCCT study involved participants aged 13 to 39 years who had been diagnosed with diabetes for at least 1 but less than 15 years and who had no, or only early signs, of diabetic retinopathy.

Outcome

The DCCT study showed that keeping blood glucose levels as close to normal as possible slows the onset and progression of the eye, kidney, and nerve damage caused by diabetes. Furthermore, it demonstrated that any sustained lowering of blood glucose helps decrease the progression of complications, even if the patient has a history of poor control.

Following the initial findings of the DCCT study, the EDIC study has found that intensive diabetes therapy had long-term beneficial effects on the risk of cardiovascular disease in patients with type 1 diabetes and that the differences in outcomes between the intensive and conventional therapy groups persist after long-term study. The EDIC follow-up is ongoing.